Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S52: Quantum Network and Quantum CommunicationFocus
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Sponsoring Units: GQI Room: 399 |
Thursday, March 16, 2017 11:15AM - 11:51AM |
S52.00001: Reflections on Quantum Data Hiding Invited Speaker: Andreas Winter Quantum data hiding, originally invented as a limitation on local operations and classical communications (LOCC) in distinguishing globally orthogonal states, is actually a phenomenon arising generically in statistics whenever comparing a `strong' set of measurements (\emph{i.e.}, decision rules) with a `weak' one. The classical statistical analogue of this would be secret sharing, in which two perfectly distinguishable multi-partite hypotheses appear to be indistinguishable when accessing only a marginal. The quantum versions are richer in that for example LOCC allows for state tomography, so the states cannot be come perfectly indistinguishable but only nearly so, and hence the question is one of efficiency. I will discuss two concrete examples and associated sets of problems: \\ 1. Gaussian operations and classical computation (GOCC): Not very surprisingly, GOCC cannot distinguish optimally even two coherent states of a single mode [Takeoka \&{} Sasaki, PRA 78:022320, 2008]. Here we find states, each a mixture of multi-mode coherent states, which are almost perfectly distinguishable by suitable measurements, by when restricted to GOCC, i.e. linear optics and post-processing, the states appear almost identical. The construction is random and relies on coding arguments. Open questions include whether there one can give a constructive version of the argument, and whether for instance even thermal states can be used, or how efficient the hiding is. \\ 2. Local operation and classical communication (LOCC): It is well-known that in a bipartite dxd-system, asymptotically $\log d$ bits can be hidden [Hayden \emph{et al.}, CMP 250:371–391, 2004]. Here we show for the first time, using the calculus of min-entropies, that this is asymptotically optimal. In fact, we get bounds on the data hiding capacity of any preparation system; these are however not always tight. While it is known that data hiding by separable states is possible (i.e. the state preparation can be done by LOCC), it is open whether the optimal information efficiency of (asymptotically) log d bits can be achieved by separable states. [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:03PM |
S52.00002: Symmetric Extendability of Quantum States, Bound Secrecy, and the Extreme Limits of Quantum Key Distribution Sumeet Khatri, Norbert Lutkenhaus Bound secret information is classical information that contains secrecy but from which secrecy cannot be extracted. The existence of bound secret information is currently unproven, and in this work we provide strong analytical and numerical evidence for its existence. Our work is tied to the noise-tolerance thresholds of quantum key distribution (QKD) protocols with public classical communication in which the classical data arises from measurement of quantum states.\\ First, we show how symmetric extendability of quantum states is related to distilling secret key from classical data. We then show how the existence of successful two-way classical protocols can be simplified to breaking the symmetric extendability through post-selection on error-correction codes. We show that repetition codes reproduce the known results on the noise-tolerance of two-way protocols in QKD and provide analytical and numerical evidence that they are optimal. For QKD protocols using a six-state setup, this means that the domain of bound secret information is characterized by a quantum bit-error rate between 27.6\% and 33.3\%. [Preview Abstract] |
Thursday, March 16, 2017 12:03PM - 12:15PM |
S52.00003: Quantum internet: the certifiable road ahead David Elkouss, Victoria Lipinska, Kenneth Goodenough, Filip Rozpedek, Norbert Kalb, Suzanne van Dam, Thinh Le Phuc, Glaucia Murta, Peter Humphreys, Tim Taminiau, Ronald Hanson, Stephanie Wehner A future quantum internet enables quantum communication between any two points on earth in order to solve problems which are provably impossible using classical communication. The most well-known application of quantum communication is quantum key distribution, which allows two users to establish an encryption key. However, many other applications are known ranging from protocols for clock synchronization, extending the baselines of telescopes to exponential savings in communication. Due to recent technological progress, we are now on the verge of seeing the first small-scale quantum communication networks being realized. Here, we present a roadmap towards the ultimate form of a quantum internet. Specifically, we identify stages of development that are distinguished by an ever increasing amount of functionality. Each stage supports a certain class of quantum protocols and is interesting in its own right. What's more, we propose a series of simple tests to certify that an experimental implementation has achieved a certain stage. Jointly, the stages and the certification tests will allow us to track and benchmark experimental progress in the years to come. [Preview Abstract] |
Thursday, March 16, 2017 12:15PM - 12:27PM |
S52.00004: Certification of quantum network functionality based on multi-round teleportation Victoria Lipinska, Le Phuc Thinh, Stephanie Wehner Quantum communication is a core element of quantum information science. The most general communication scenario involves separated nodes exchanging quantum information at a large distance, which can define a quantum network. It has been shown that various operational stages of network functionality can be tested. In particular, it is known that in certain networks nodes can certify storage of a quantum system for a given time. On the other hand, in some networks a local control over the system can be maintained. Here we focus on a quantum network which combines the two functionalities. We propose a simple test which we call lifetime and control test, that provides an explicit certification of attainment of both tasks. Specifically, we present a protocol based on multi-round teleportation whose successful realization guarantees the desired functionality of the network. We demonstrate its performance and adapt the protocol to experimentally feasible scenarios employing imperfect memory. We also provide explicit parameters for estimation of the quality of a memory in the presence of local control, based on the probability of successful performance of the protocol. [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 12:39PM |
S52.00005: Realistic parameter regimes for a single sequential quantum repeater node Kenneth Goodenough, Filip Rozpedek, Jeremy Ribeiro, Valentina Caprara Vivoli, Andreas Reiserer, David Elkouss, Stephanie Wehner The goal of a quantum repeater is to be able to communicate more efficiently than it is possible without a quantum repeater. In particular, it is natural to compare the rate at which one can generate secret key with an implementation of a quantum repeater and the theoretical maximum rate without one. By modeling such a repeater implementation, it is possible to find parameter regimes where repeaters would give a benefit over direct communication. Here, we model a specific, but general, setup for a repeater which can be implemented using, for example, nitrogen-vacancy centers. Furthermore, we also introduce three new tools to assess the performance of repeaters. The first of these tools is a series of benchmarks based on finite-energy considerations and to what one considers as losses in the setup. The second tool is the introduction of a cut-off, which reduces the effect of decoherence in systems such as nitrogen-vacancy centers by implementing a maximum on the allowed storage time. Finally, we analyze the repeater setup when advantage distillation is used, which is a more advanced type of classical post-processing. Using these tools, we find realistic parameters for which it is possible to beat the mentioned benchmarks, guiding the way towards implementing quantum repeaters. [Preview Abstract] |
Thursday, March 16, 2017 12:39PM - 12:51PM |
S52.00006: Applications of a Circuit QED Quantum Channel Constructor Chao Shen, Kyungjoo Noh, Victor V. Albert, Stefan Krastanov, Michel H. Devoret, Robert J. Schoelkopf, S. M. Girvin, Liang Jiang Quantum channels can describe all transformations allowed by quantum mechanics. We provide an explicit universal protocol to construct all possible quantum channels, using a single qubit ancilla with quantum non-demolition readout and adaptive control. Our construction is efficient in both physical resources and circuit depth, and can be demonstrated using superconducting circuits and various other physical platforms. There are many applications of quantum channel construction, including system stabilization and quantum error correction, Markovian and exotic channel simulation, implementation of generalized quantum measurements and more general quantum instruments. Efficient construction of arbitrary quantum channels opens up exciting new possibilities for quantum control, quantum sensing and information processing tasks. [Preview Abstract] |
Thursday, March 16, 2017 12:51PM - 1:03PM |
S52.00007: BB84 with Weak Measurements, Greater Security with Fewer Assumptions James Troupe, Jacob Farinholt Detector blinding attacks on prepare-and-measure QKD protocols allow an eavesdropper to take control of Bob's measurement device and mask her interactions with the signals. Measurement-device-independent QKD (MDI-QKD) was developed to avoid this ``detector loophole'' by altogether eliminating Bob's detectors. Parameter estimation and key extraction is performed based on the results of a joint Bell measurement on both Alice and Bob's signals. While this resolves the security loophole, the need for a Bell measurement requires both signals to arrive in the same timing window, leading to significant engineering challenges and/or a severe reduction in secure key rates. Here we propose a simpler method to avoid the detector loophole in a prepare-and-measure scenario. Namely, we show that it is possible to completely separate the parameter estimation from its dependency on Bob's measurement basis by making weak measurements immediately prior to Bob's detection and averaging these results conditioned only on the source. We show that this new protocol is as secure as MDI-QKD under detector attacks, is practical to implement, and provides a secure key rate equivalent to that promised by the original BB84 protocol. [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:15PM |
S52.00008: Long distance quantum communication with quantum Reed-Solomon codes Sreraman Muralidharan, Chang-Ling Zou, Linshu Li, Liang Jiang We study the construction of quantum Reed Solomon codes from classical Reed Solomon codes and show that they achieve the capacity of quantum erasure channel for multi-level quantum systems. We extend the application of quantum Reed Solomon codes to long distance quantum communication, investigate the local resource overhead needed for the functioning of one-way quantum repeaters with these codes, and numerically identify the parameter regime where these codes perform better than the known quantum polynomial codes and quantum parity codes . Finally, we discuss the implementation of these codes into time-bin photonic states of qubits and qudits respectively, and optimize the performance for one-way quantum repeaters. [Preview Abstract] |
Thursday, March 16, 2017 1:15PM - 1:27PM |
S52.00009: Bounds on negativity for the success of quantum teleportation of qutrit-qubit system paulson K G, S.V.M Satyanarayana In the original protocol Bennet et.al., used maximally entangled pure states as quantum channel to teleport unknown states between distant observers with maximum fidelity. Noisy quantum channel can be used for imperfect teleportation. Both degree of entanglement and mixedness decide the success of teleportation in the case of mixed entangled quantum channel. . In one of our previous works, we discussed the existence of lower bound below which ,state is useless for quantum teleportation in the measure of entanglement for a fixed value of fidelity, and this lower bound decreases as rank increases for two-qubit system. We use negativity as the measure of entanglement. . In this work, we consider a qutrit-qubit system as quantum channel for teleportation, and study how the negativity and rank affect the teleportation fidelity for a class of states. We construct a new class of mixed entangled qutrit-qubit states as quantum channel, which is a convex sum of orthonormal maximally entangled and separable pure states. The classical limit of fidelity below which state is useless for quantum teleportation is fixed as 2/3. We numerically generate 30000 states and estimate the value of negativity below which each rank mixed state is useless for quantum teleportation. We also construct rank dependant boundary states by choosing appropriate eigen values, which act as upper bound for respective rank states. [Preview Abstract] |
Thursday, March 16, 2017 1:27PM - 1:39PM |
S52.00010: Quantum Counterfactual Information Transmission Without a Weak Trace David Arvidsson Shukur, Crispin Barnes The classical theories of communication rely on the assumption that there has to be a flow of particles from Bob to Alice in order for him to send a message to her. We have developed a quantum protocol that allows Alice to perceive Bob's message ``counterfactually". That is, without Alice receiving any particles that have interacted with Bob. By utilising a setup built on results from interaction-free measurements and the quantum Zeno effect, we outline a communication protocol in which the information travels in the opposite direction of the emitted particles. In comparison to previous attempts on such protocols, this one is such that a weak measurement at the message source would not leave a weak trace that could be detected by Alice's receiver. Whilst some interaction-free schemes require a large number of carefully aligned beam-splitters, our protocol is realisable with two or more beam-splitters. Furthermore, we outline how Alice's obtained classical Fisher information between a weak variable at Bob's laboratory is negligible in our scheme. We demonstrate this protocol by numerically solving the time-dependent Schr\"odinger Equation (TDSE) for a Hamiltonian that implements this quantum counterfactual phenomenon. [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 1:51PM |
S52.00011: Measurement-based quantum teleportation on finite AKLT chains Akihiko Fujii, David Feder In the measurement-based model of quantum computation, universal quantum operations are effected by making repeated local measurements on resource states which contain suitable entanglement. Resource states include two-dimensional cluster states and the ground state of the Affleck-Kennedy-Lieb-Tasaki (AKLT) state on the honeycomb lattice. Recent studies suggest that measurements on one-dimensional systems in the Haldane phase teleport perfect single-qubit gates in the correlation space, protected by the underlying symmetry. As laboratory realizations of symmetry-protected states will necessarily be finite, we investigate the potential for quantum gate teleportation in finite chains of a bilinear-biquadratic Hamiltonian which is a generalization of the AKLT model representing the full Haldane phase. [Preview Abstract] |
Thursday, March 16, 2017 1:51PM - 2:03PM |
S52.00012: Quantum enhanced interferometry using imperfect repeaters. siddhartha santra, Brian Kirby, Alejandra Maldonado-Trapp, Michael Brodsky The baseline size of telescopic arrays used in stellar interferometry - maximum distance between two telescopes in the array - determines the angular resolution of the array. Larger baselines lead to finer resolution of the intensity distribution of the distant extended source. Since interferometry relies on bringing the photons, collected at the distant telescopes, together for eventual interference – their loss in the connecting optical channels limits how far the baselines may be practically extended. One can use shared entangled states between the nodes of a quantum network to mitigate the effects of photon loss that leads to a loss in the sensitivity of the telescopic array. We show how using distributed entangled quantum states between two telescopes - the size of the baselines can be increased. This leads to improved angular resolution of the telescope array in the weak source regime – where the light from distant sources may be considered at the single-photon level. In our work we consider quantum networks with access to imperfectly entangled quantum states and determine their utility towards optical interferometry of signals from distant sources. [Preview Abstract] |
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